Boeing shares fell Wednesday after the plane maker withdrew its contract offer for striking machinists and S&P Global put its bond rating on a watch list.

Boeing and the union that represents 33,000 striking employees at the company say talks between the two have broken down and no new talks are scheduled.

Last month, all three major ratings agencies including S&P had warned that a prolonged strike at Boeing's factories in the U.S. West Coast may lead to a ratings downgrade, a heada

Boeing Co. is on the verge of a significant financial setback as S&P Global Ratings considers downgrading the company’s credit rating to junk status. This looming downgrade is driven by Boeing’s escalating cash requirements and the prolonged strike by machinists that has severely impacted the company’s production capabilities.